The American Civil Liberties Union (ACLU) in Mississippi told BuzzFeed News Thursday that they were concerned about the legality of the policy.

"We have been contacted by family members who would be impacted, we have reviewed the policy, and we have serious concerns regarding its legality," the ACLU said in its statement. "We are considering all options.”

David Fathi, the Director of the ACLU’s National Prison Project, told BuzzFeed News the policy was "completely unprecedented" and "almost certainly unconstitutional."

"In my 20 years of working in prisons and jails, I have never seen a policy that even approaches the level of restrictiveness of this policy," Fathi said.

He said the by forbidding pastors from visiting inmates, the policy likely violated a federal law — the Religious Land Use and Institutionalized Persons Act — that protects the religious exercise of prisoners. It was also in possible violation of the First Amendment, Fathi said.

Blake Feldman, an ACLU advocate, first tweeted a photo of the new policy posted in the South Mississippi Correctional Institution. He said it was sent to him by the fiancée of an inmate at the prison.

The new policy said visitors were limited to the inmate's immediate family members, defined by the Mississippi Department of Corrections (MDOC) to include only spouses, children, stepchildren raised prior to age 12, brothers, sisters, parents, grandparents, grandchildren, documented stepparents, foster parents, or relatives acting as surrogate parents.

The new policy, announced Wednesday, was to go into effect on Thursday.

Although the notice appeared to be posted at the prison and stated that the policy was effective Thursday, a spokesperson for the MDOC told BuzzFeed News that the policy was "not finalized."

Jasmine Cole, the MDOC's spokesperson, first told BuzzFeed News that the policy was "under review" and was not "finalized."

In a later statement, she said, "The recent change in the visitation policy was prompted by security violations that are being investigated. Upon completion of the investigation, MDOC will consider re-evaluating the policy."

She said visitation on Sept. 3 and 4 would not be affected.

A spokesperson for the superintendent of the South Mississippi Correctional Institute referred all questions to the MDOC.

"I can't breathe," the inmate's fiancée told Feldman, according to his tweets. "This is so unfair."